Error 13 after moving MySQL datadir outside /var/lib, no error when staying inside /var/lib

Recently I installed MySQL, version 8.4.3, on my Ubuntu 22.04.5 OS. I then changed the datadir from /var/lib/mysql to new location /media/cat/hekla/mysql, following the approach described in Ergest Basha's answer to the question [Error after changing/moving mysql datadir in ubuntu sys](https://dba.stackexchange.com/questions/327307/error-after-changing-moving-mysql-datadir-in-ubuntu-sys) . Restarting MySQL however fails, and systemctl status mysql.service tells me: × mysql.service - MySQL Community Server Loaded: loaded (/lib/systemd/system/mysql.service; enabled; vendor preset: enabled) Active: failed (Result: exit-code) since Wed 2024-11-06 11:18:27 CET; 2min 31s ago Docs: man:mysqld(8) http://dev.mysql.com/doc/refman/en/using-systemd.html Process: 11628 ExecStartPre=/usr/share/mysql-8.4/mysql-systemd-start pre (code=exited, status=0/SUCCESS) Process: 11667 ExecStart=/usr/sbin/mysqld (code=exited, status=1/FAILURE) Main PID: 11667 (code=exited, status=1/FAILURE) Status: "Server shutdown complete (with return value = 1)" Error: 13 (Permission denied) CPU: 292ms nov 06 11:18:27 golem mysqld: 2024-11-06T10:18:27.019616Z 0 [System] [MY-010116] [Server] /usr/sbin/mysqld (mysqld 8.4.3) starting as process 11667 nov 06 11:18:27 golem mysqld: 2024-11-06T10:18:27.021198Z 0 [Warning] [MY-010091] [Server] Can't create test file /media/cat/hekla/mysql/mysqld_tmp_file_case_insensitive_test.lower-test nov 06 11:18:27 golem mysqld: 2024-11-06T10:18:27.021202Z 0 [Warning] [MY-010159] [Server] Setting lower_case_table_names=2 because file system for /media/cat/hekla/mysql/ is case insensitive nov 06 11:18:27 golem mysqld: 2024-11-06T10:18:27.021216Z 0 [ERROR] [MY-013276] [Server] Failed to set datadir to '/media/cat/hekla/mysql/' (OS errno: 13 - Permission denied) nov 06 11:18:27 golem mysqld: 2024-11-06T10:18:27.021275Z 0 [ERROR] [MY-010119] [Server] Aborting nov 06 11:18:27 golem mysqld: 2024-11-06T10:18:27.021685Z 0 [System] [MY-010910] [Server] /usr/sbin/mysqld: Shutdown complete (mysqld 8.4.3) MySQL Community Server - GPL. nov 06 11:18:27 golem mysqld: 2024-11-06T10:18:27.021689Z 0 [System] [MY-015016] [Server] MySQL Server - end. nov 06 11:18:27 golem systemd: mysql.service: Main process exited, code=exited, status=1/FAILURE nov 06 11:18:27 golem systemd: mysql.service: Failed with result 'exit-code'. nov 06 11:18:27 golem systemd: Failed to start MySQL Community Server. Interestingly, I made a backup copy /var/lib/mysql.bak of /var/lib/mysql, and when I change the datadir to this backup directory then it does work! Any ideas what the problem can be, and how to solve it? Any other things that could require adjustment, perhaps involving location /var/lib/ considering that the backup directory sitting next to the original does work? The content of /etc/apparmor.d/usr.sbin.mysqld is: include /usr/sbin/mysqld { #include #include #include #include #include # Allow system resource access /sys/devices/system/cpu/ r, /sys/devices/system/node/ r, /sys/devices/system/node/** r, /proc/*/status r, capability sys_resource, capability dac_override, capability setuid, capability setgid, capability sys_nice, # Allow network access network tcp, /etc/hosts.allow r, /etc/hosts.deny r, # Allow config access /etc/mysql/** r, # Allow pid, socket, socket lock and other file access /run/mysqld/* rw, /var/run/mysqld/* rw, # Allow systemd notify messages /{,var/}run/systemd/notify w, # Allow execution of server binary /usr/sbin/mysqld mr, /usr/sbin/mysqld-debug mr, # Allow plugin access /usr/lib/mysql/plugin/ r, /usr/lib/mysql/plugin/*.so* mr, # Allow error msg and charset access /usr/share/mysql/ r, /usr/share/mysql/** r, /usr/share/mysql-8.4/ r, /usr/share/mysql-8.4/** r, # Allow data dir access /var/lib/mysql/ r, /var/lib/mysql/** rwk, # /var/lib/mysql.bak/ r, # /var/lib/mysql.bak/** rwk, # /media/cat/hekla/mysql/ r, # /media/cat/hekla/mysql/** rwk, # Allow data files dir access /var/lib/mysql-files/ r, /var/lib/mysql-files/** rwk, # Allow keyring dir access /var/lib/mysql-keyring/ r, /var/lib/mysql-keyring/** rwk, # Allow log file access /var/log/mysql/ r, /var/log/mysql/** rw, # Allow access to openssl config /etc/ssl/openssl.cnf r, # Site-specific additions and overrides. See local/README for details. #include }